ok...we seem to be on two different pages....I am using this website....

http://www.poolandspachemicals.co.uk/volcalc.htm

take each part of the pool as two rectangles....

first rectangle...21 x 22 x 3 (LXWXD) = 10367 us gallons
second rectangle....20 X 18 X 8 (starts at 6 ends at 8) = 18850 us gallons

total- 29,000 gallons...take out the steps...curves of walls, etc...about 27,500 gallons...can you walk me through your calcs....in the mean time, I will try to find the pool info through the packet we were given from previous owner...